The present invention generally relates to subsurface apparatuses used in the petroleum production industry. More particularly, the present invention relates to an apparatus and method to conduct fluid through subsurface apparatuses, such as a subsurface safety valve, to a downhole location. More particularly still, the present invention relates to apparatuses and methods to install a subsurface safety valve incorporating a bypass conduit allowing communications between a surface station and a lower zone regardless of the operation of the safety valve.
Various obstructions exist within strings of production tubing in subterranean wellbores. Valves, whipstocks, packers, plugs, sliding side doors, flow control devices, expansion joints, on/off attachments, landing nipples, dual completion components, and other tubing retrievable completion equipment can obstruct the deployment of capillary tubing strings to subterranean production zones. One or more of these types of obstructions or tools are shown in the following United States patents which are incorporated herein by reference: Young, U.S. Pat. No. 3,814,181; Pringle, U.S. Pat. No. 4,520,870; Carmody et al., U.S. Pat. No. 4,415,036; Pringle, U.S. Pat. No. 4,460,046; Mott, U.S. Pat. No. 3,763,933; Morris, U.S. Pat. No. 4,605,070; and Jackson et al., U.S. Pat. No. 4,144,937. Particularly, in circumstances where stimulation operations are to be performed on non-producing hydrocarbon wells, the obstructions stand in the way of operations that are capable of obtaining continued production out of a well long considered depleted. Most depleted wells are not lacking in hydrocarbon reserves, rather the natural pressure of the hydrocarbon producing zone is so low that it fails to overcome the hydrostatic pressure or head of the production column. Often, secondary recovery and artificial lift operations will be performed to retrieve the remaining resources, but such operations are often too complex and costly to be performed on all wells. Fortunately, many new systems enable continued hydrocarbon production without costly secondary recovery and artificial lift mechanisms. Many of these systems utilize the periodic injection of various chemical substances into the production zone to stimulate the production zone thereby increasing the production of marketable quantities of oil and gas. However, obstructions in the producing wells often stand in the way of deploying an injection conduit to the production zone so that the stimulation chemicals can be injected. While many of these obstructions are removable, they are typically components required to maintain production of the well so permanent removal is not feasible. Therefore, a mechanism to work around them would be highly desirable.
The most common of these obstructions found in production tubing strings are subsurface safety valves. Subsurface safety valves are typically installed in strings of tubing deployed to subterranean wellbores to prevent the escape of fluids from the wellbore to the surface. Absent safety valves, sudden increases in downhole pressure can lead to disastrous blowouts of fluids into the atmosphere. Therefore, numerous drilling and production regulations throughout the world require safety valves be in place within strings of production tubing before certain operations are allowed to proceed.
Safety valves allow communication between the isolated zones and the surface under regular conditions but are designed to shut when undesirable conditions exist. One popular type of safety valve is commonly referred to as a surface controlled subsurface safety valve (SCSSV). SCSSVs typically include a closure member generally in the form of a circular or curved disc, a rotatable ball, or a poppet, that engages a corresponding valve seat to isolate zones located above and below the closure member in the subsurface well. The closure member is preferably constructed such that the flow through the valve seat is as unrestricted as possible. Usually, the SCSSVs are located within the production tubing and isolate production zones from upper portions of the production tubing. Optimally, SCSSVs function as high-clearance check valves, in that they allow substantially unrestricted flow therethrough when opened and completely seal off flow in one direction when closed. Particularly, production tubing safety valves prevent fluids from production zones from flowing up the production tubing when closed but still allow for the flow of fluids (and movement of tools) into the production zone from above.
SCSSVs normally have a hydraulic control line extending from the valve, said hydraulic control line disposed in an annulus formed by the well casing and the production tubing and extending from the surface. Pressure in the hydraulic control line opens the valve allowing production or tool entry through the valve. Any loss of pressure in the hydraulic control line closes the valve, prohibiting flow from the subterranean formation to the surface.
Closure members are often energized with a biasing member (spring, hydraulic cylinder, gas charge and the like, as well known in the industry) such that in a condition with no pressure, the valve remains closed. In this closed position, any build-up of pressure from the production zone below will thrust the closure member against the valve seat and act to strengthen any seal therebetween. During use, closure members are opened to allow the free flow and travel of production fluids and tools therethrough.
Formerly, to install a chemical injection conduit around a production tubing obstruction, the entire string of production tubing had to be retrieved from the well and the injection conduit incorporated into the string prior to replacement often costing millions of dollars. This process is not only expensive but also time consuming, thus it can only be performed on wells having enough production capability to justify the expense. A simpler and less costly solution would be well received within the petroleum production industry and enable wells that have been abandoned for economic reasons to continue to operate.